Next generation ultra-broadband elastic optical networks maximize system-bandwidth utilization based on flexible diverse traffic demands accommodation. Research on novel network architectures and system components such as datarate variable transponders and hybrid amplification schemes are needed to allow geographical context adjustability as well as capacity system upgradeability from Gbps to Tbps. In this paper we report experimental validations on deployed Brazilian optical fiber of a data-rate variable transmitter feasible for both metro and long-haul applications. The developed transmission system exhibits spectral efficiencies of 4.58, 6.25 and 3.41 b/s/Hz for 1400, 700 and 4900 km of optical transmission respectively.
The digitally modulated signals spectral density depends directly on pulse format used for information symbols
transmission. The modulated signal spectral occupancy can be modified according to the channel frequency response to
facilitate information retrieval at the receiver. New generation of coherent optical transmission systems operating at high
rates are subject to various bandwidth restrictions aspects, such as electronic components limitations and optical filtering
via ROADMs deployed on networks. As noted in technical literature, the RZ pulse formats have some advantages
compared to traditional NRZ pulses in optical fiber transmissions. In particular, RZ pulses have a better performance in
situations where nonlinear effects of the fiber severely impact the quality of transmission. Among other situations, this
occurs in systems that employ modulation formats for high order QAM (16QAM, 64QAM, etc.). Moreover, since RZ
pulses have shorter duty cycle, temporal spread of the transmitted symbols causes less performance degradation due to
ISI compared with NRZ pulses. This report presents results of experiments carried out in a 226 km recirculation loop, to
evaluate the performance of NRZ, RZ 67%, 50% RZ and RZ 33% pulse shapes in a transmission of DP-16QAM (or
PDM-16QAM). As application it is proposed and experimentally demonstrated a transmission system that employ 28
GBaud dual carrier PDM-16QAM channels operating with a total line rate of 448 Gb/s each, utilizing RZ pulse format
and carrier narrow pre-filtering to increase spectral efficiency of transmission, aggregating a 400G channel in a 75 GHz
WDM grid.
The photoacoustic technique is based on the absorption of modulated light by a sample and subsequent heat generation. This generates thermal waves that propagate in the surrounding media. According to the Rosencwaig-Gersho Model, such waves produce the pressure oscillation detected as the photoacoustic signal. This technique allows the spectroscopic characterization of multilayer systems: as the thermal diffusion length varies with the modulation frequency of the absorbed light, the depth profile of a sample can be studied by the analysis of the photoacoustic signal at different modulation frequencies. In this work, photoacoustic spectroscopy was used to characterize different human skin samples. Measurements were performed at 70Hz and 17Hz, using a 1000W Xe arc lamp as the light source, for wavelengths between 240nm and 700nm. Skin samples were about 0,5cm diameter. It was possible to obtain the photoacoustic absorption spectra of the stratum corneum and of a deeper layer of epidermis; when the lower modulation frequency is utilized, photoacoustic spectroscopy characterizes the absorption of the whole epidermis, because in this case the thermal diffusion length is thicker than that of the stratum corneum. Photoacoustic spectroscopy was also employed to monitor the drying kinetics of the skin. This was done by analyzing the time evolution of the photoacoustic spectra of skin samples. Pre-treatment of the samples included different periods in a drying chamber. Measurements show that the photoacoustic spectra changes according to the humidity of the skin. Future work includes detailed monitoring of skin hydration.
In the photoacoustic technique, the signal is proportional to the heat produced in a sample as a consequence of modulated light absorption. This technique allows the spectroscopic characterization of multilayer systems: as the thermal diffusion length varies with the light modulation frequency, one can obtain the depth profile of the sample by analyzing the frequency-dependence of the signal. As the photoacoustic signal depends on thermal and optical properties of the sample, structural changes in the system under analysis account for signal variations in time. In this work, photoacoustic spectroscopy was used to characterize samples of sunscreen and the system formed by sunscreen plus skin. We used photoacoustic spectroscopy to monitor the absorption kinetics of sunscreen applied to samples of human skin, characterizing alterations in the human skin after application of sunscreen. Measurements used 250W Xe arc lamp as light source, for wavelengths between 240nm and 400nm. This range corresponds to most of the UV radiation that reaches Earth. Skin samples were about 0,5cm diameter. The absorption spectra of sunscreen was obtained. Finally, photoacoustics was employed to monitor the absorption kinetics of the sunscreen applied to skin samples. This was done by applying sunscreen in a skin sample and recording the photoacoustic spectra in regular time intervals, up to 90 minutes after application. According to measurements, light absorption by the system sunscreen plus skin stabilizes between 25 and 45 minutes after sunscreen application. Results show that this technique can be utilized to monitor drug delivery and farmacokinetics in skin samples.
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